Final answer:
The Marks card option specific to pie charts is 'Angle' because it defines the size of each slice to demonstrate proportions within the whole. Other options like Label, Color, and Size are not exclusive to pie charts.
Step-by-step explanation:
The Marks card option used exclusively for creating pie charts is Angle. This is because the size of each slice in a pie chart is determined by the angle of the slice, which represents the proportion of that category within the whole. Options like Label, Color, and Size can be used in various chart types, but only Angle is specific to pie charts, as it defines the pie slice's arc length proportionate to the overall 360 degrees of a circle.
When considering how to visually represent data, one could manipulate the angle to emphasize certain slices over others, just like one can manipulate the vertical axis in a bar graph to exaggerate variations in bar heights.